This invention relates to tubular rivets of the type usually used for holding together two or more sheets of material. More particularly, this invention is directed to an open end blind rivet of the type having a first flange at one end of the rivet body and utilising a headed mandrel to deform the opposed end of the rivet body to compress the sheet material between the flange of the rivet body and its deformed end.
Open end blind rivets are well known and notably those sold under the applicants trade mark POP® (registered trade mark of Emhart Inc.) as a conventional fixing mechanism for holding together two or more sheets of material. This type of blind rivet comprises of a hollow, tubular rivet body having a large flange towards one end thereof to engage with one side of a sheet material, whereby the opposed end of the tubular rivet body is passed through a preformed hole. The rivet further comprises a headed mandrel which extends through the hollow tubular rivet body with its head engaging the opposed end thereof. During setting of the blind rivet the head of the mandrel compresses the opposed end of the rivet body which is deformed towards the flange of the rivet body, to compress the sheet material therebetween. The mandrel will further comprise a weakened shank in the region of the mandrel head with a pre-determined break load allowing the mandrel to be removed from the set rivet when sufficient load is applied. This provides for a simple and inexpensive fasting means that can be applied manually and set with a suitable rivet setting tool to hold together two or more sheets of material. It is generally understood that whilst the mandrel head is drawn into the rivet, to deform the rivet when set, such engagement between the rivet head and the rivet is not airtight nor waterproof. The mandrel head is often free to move within the deformed portion of the set rivet and can occasionally be found to “rattle” within the set rivet.
Alternatively, where blind rivets are required to create a watertight or airtight seal, closed-end (or sealed) blind rivets are employed. Such closed-end blind rivets are similar to open-end blind rivets but instead of the head of the mandrel being disposed externally of a hollow tubular rivet body, the headed mandrel is retained within a closed cup shaped cylindrical tube so as to be encapsulated within the rivet body such that the rivet body has a closed end.
However, the manufacture of closed-end blind rivets is comparatively more complex and expensive whereby the large mandrel head is first received in a cup shaped preform, the resulting subassembly extruded to encapsulate the mandrel within the body of the rivet and simultaneously form the rivet body flange. Not only is this process more expensive but requires a high degree of tooling accuracy and manufacturing skill to prevent damage to the mandrel and the associated manufacturing tooling. A further drawback to this type of manufactured blind rivet is a limitation to the length of the rivet body and/or the length of the mandrel that can be made on current manufacturing machinery and if suitable machinery were available the cost of that machinery plus the attendant slowness of the process would render the resulting closed end rivet prohibitively expensive.
It is so often desirable to use closed-end rivets in situations where airtight or watertight joints are required. However, where such rivets are required to secure thick workpieces or where the rivet is inserted into narrow recesses or channels difficulties can arise due to the limitation of the length of the rivet body or the length of the mandrel thus restricting the applicability of closed-end rivets in such applications. Conventional setting tools for blind rivets to be set in deep and narrow recesses require a relatively long mandrel in order to grip and set the rivet. Thus current technology does not provide for blind rivets capable of application in deep narrow recesses or thick joints and being able to consistently achieve a watertight or airtight seal.
It is therefore an object of the present invention to alleviate the aforementioned problems and to provide an open-end blind rivet capable of providing an airtight or watertight seal when set.